Steve is a horticulturist of sorts. He raises orchids, Japanese maples, and other plants at his southern Rhode Island home. Tending the plants helps ease his rheumatoid arthritis (RA) pain, he says. But the garden offers more than Zen; he grows one plant -- marijuana -- specifically to relieve RA pain and discomfort.

"If my pain is at a 10, it will take it down to a 6 or 6.5," he says. "I’m an old-man weight lifter. After I smoke I am able to work my shoulders and arms to keep my joints healthy. It gives me the desire and ability to get through a workout."

Steve has had permission to grow marijuana for medicinal purposes since 2006. He smokes it and cooks it in butter (for baking) and makes THC-containing solutions called tinctures (which can be added to foods and drinks) for himself and five other patients with various medical conditions. His home state is 1 of 16, along with the District of Columbia, where marijuana is permitted for medicinal use.

Cannabis may be useful for people with RA and other chronic pain conditions because it can alleviate pain, reduce inflammation, and promote sleep. But unlike other pain-causing conditions, such as osteoarthritis, RA is associated with a higher risk of lung problems and heart attacks. (RA is an autoimmune condition that attacks the joints and causes multiple health problems.)

It’s not clear if smoking marijuana is a relatively safe pain reliever for people with RA, or if it could increase the risk of RA-associated conditions. And if cannabis is safe, it’s still debatable whether it’s safer to take it as a pill or mouth spray rather than smoking it. Smoking marijuana raises the heart rate and one study found that heart-attack risk rises fivefold in the hour after lighting up, according to the National Institute on Drug Abuse.

Medical marijuana remains controversial -- and thus under-studied -- in part because it is the most commonly abused illicit drug in the U.S.

How marijuana works

There are hundreds of chemicals in marijuana, but the best known is delta-9-tetrahydrocannabinol, or THC. THC is what produces the high that comes with smoking or eating products made from marijuana.

But THC also binds with receptors in the brain that produce an analgesic affect. It may also reduce anxiety experienced by some people dealing with chronic pain.

Marijuana is typically smoked, which produces the most rapid delivery into the bloodstream, says Kathryn Cunningham, Ph.D., director of the Center for Addiction Research at the University of Texas Medical Branch, in Galveston.

It can also be taken through vaporization (heated into a mist and inhaled), and in edible products, such as baked goods and tinctures, which take longer to have an effect because they have to be broken down in the stomach, Cunningham says.

There are also drugs such as Marinol (dronabinol) and Cesamet (nabilone), which are synthetic versions of THC in pill form that are available by prescription for AIDS patients and cancer patients undergoing chemotherapy, and a newer product called Sativex, a mouth spray with THC and cannabidiol. Sativex is not yet available in the United States, but is used in Canada and Europe for pain relief in people with cancer and multiple sclerosis.

Marijuana is illegal on the federal level, but medicinal marijuana is permitted in some states, including Alaska, Arizona, California, Colorado, Delaware, Hawaii, Maine, Michigan, Montana, Nevada, New Jersey, New Mexico, Oregon, Rhode Island, Vermont, and Washington. Each state has its own guidelines including conditions it can be used for and possession limits (which range from 1 ounce to 24 ounces). Marijuana can be purchased through dispensaries, but most states also allow people to grow the product.

Research is limited

Medicinal marijuana isn’t regulated by the Food and Drug Administration, and there aren’t large-scale studies of its safety and efficacy for chronic pain conditions. (It doesn’t help that there are few manufacturers to fund research.) But there have been some small-scale studies looking at its use.

A 2006 study in Rheumatology looked at 58 RA patients over a five-week period. They were split into two groups -- one taking Sativex and the other a placebo. The group on Sativex had improvements in "morning pain on movement" and sleep quality compared to placebo users. (The study was funded by GW Pharmaceuticals, which makes Sativex.)

"This is a good example of how to answer the question with scientifically sound experiments," Cunningham says, adding that larger studies are needed. "We don’t know how the drug affects the disease process, but it does seem to have a positive analgesic effect on RA."

Doctors at the University of Toronto and Dalhousie University in Halifax reviewed 18 clinical trials that included 766 people between 2003 and 2010. The trials studied the use of cannabis -- either smoked or in THC-based prescription products -- as a medical therapy for non-cancer-related pain, most often neuropathic pain (chronic pain that is usually due to nerve damage).

Fifteen of the trials found that it worked better than a placebo for pain relief and four trials found that it improved patients’ sleep. A majority of the studies found that side effects like sedation, dry mouth, dizziness, and disturbed concentration were mild enough that people did not drop out of the studies.

However, the analysis included only one study of RA patients -- the same 2006 Sativex study -- so it could not determine if the long-term use of smoked marijuana was associated with a higher risk of heart or lung complications.

Potential health risks

Smoking marijuana can increase a person’s heart rate for up to three hours, according to the National Institute on Drug Abuse. Marijuana also contains carcinogens (possibly 50 percent to 70 percent more than cigarettes), making smoking potentially harmful to RA patients, who may already suffer from lung problems. The Institute on Drug Abuse, however, reported that no studies have linked marijuana use to lung or upper respiratory cancers.

Safety of unregulated products is also always a concern. John Oram, Ph.D., cofounder of CW Analytical, a California-based scientific lab that tests medical marijuana products for safety, quality, and potency, says that more than 90 percent of what is on the market is safe.

"But about 10 percent or less is dangerous, and we don’t know how unsafe it is and what problems it may cause," he says. Oram adds that labs like CW Analytical empower patients and doctors to make informed decisions about their alternative medicine options.

Hazards of these products can include things like bacteria and mold, which would be illegal to sell in regulated food items. Some products may also be prepared in kitchens that aren’t licensed, may not adhere to refrigeration schedules, or may be made with allergens like peanuts, but not labeled as such.

Oram says products should be tested within seven to eight weeks of purchase because that is the shelf life of cannabis. The dispensaries should have records of the date a product was tested for mold, yeast, bacteria, and pesticides, as well as its potency (or amount of THC).

Not all doctors prescribe medicinal marijuana, even in states where it is permitted. Ogechi "Helen" Mbakwe, M.D., from Central Washington Internal Medicine and Endocrine Center, in Yakima, doesn’t.

Dr. Mbakwe is uncomfortable with the lack of control and regulation of medicinal marijuana. She says other medications, like methotrexate, treat the autoimmune disease at the root of the problem, and in turn can control pain and inflammation in combination with pain medications like nonsteroidal anti-inflammatory drugs . (Methotrexate and other drugs are known as disease-modifying antirheumatic drugs, or DMARDs, because they can actually slow down or prevent RA’s damaging effect on the body.)

On the other hand, while marijuana may help with pain symptoms, it does nothing for the disease progression or organ damage, Dr. Mbakwe says.

"If we mask these [symptoms] by giving them marijuana and giving them euphoria, the disease progression will keep getting worse and things like organ damage and severe problems will still occur," she notes.

Steve, who has RA and lost one of his kidneys in 2004 after being diagnosed with cancer, feels he doesn’t have a lot of choices to manage his pain. Many RA medications can be harmful to the kidneys, and that is one reason he says he opts for marijuana to treat his symptoms.

Patients with kidney problems can still take DMARDs as long as their dose is adjusted and they are monitored closely, Dr. Mbakwe says. "DMARDs are not simply pain medications and are not interchangeable with pain medications. So the question of exchanging an RA medication with marijuana should not arise."

Another problem that Dr. Mbakwe encounters is that, even though she doesn’t recommend marijuana to her RA patients, she has many who use it for pain, and she says these patients often have a tendency to abuse narcotics.

"Most patients looking for this have other chronic pain issues and are likely on other controlled substances," Dr. Mbakwe says. "It can be difficult to see who has a tendency toward abuse potential."

Gregory A. Smith, M.D., medical director of the Los Angeles–based Comprehensive Pain Relief Group, is a pain management and addiction specialist. He says marijuana is not a drug, like methamphetamine, that you take once and are physically dependent upon. "Marijuana does not have that kind of chemical reaction in the brain," he says. "It is safer than a lot of the prescription narcotics that I detox people from."

About 28 million people try marijuana each year, and only between 8 percent and 10 percent of users exhibit addictive behavior like drug seeking, Cunningham says. "What we need to know is if it is addicting in pain patients and is it more so than opiate medications," which are commonly used to treat chronic pain, she says.

In the meantime, some patients will continue to use marijuana even though large studies haven’t tested its safety and efficacy.

Steve, who has been using marijuana for 30 years (long before it was medically legal), smokes a bowl and a half every day and more at night. He says this helps him sleep and relieves pain, and he hasn’t experienced any major side effects over the years, but admits that it can precipitate what he calls "couch lock."